Ninety-seven percent of right-handed (RH) individuals develop speech and language processing in the left (dominant) hemisphere of the brain, while the "minor" hemisphere controls emotional behavior. We have speculated that a hypothetical gene, RGHT, functions to specify left-brain dominance, resulting in developing the right-handed preference. We have been collecting blood samples and cheek swabs from specific families in order to genetically map the hypothesized RGHT gene. We have now collected enough samples and the next stage is to use these samples for mapping via the sib-pair method. We have published our random recessive model in which individuals with the nonfunctional recessive allele on both homologs have a 50:50 chance of either being RH or left-handed (LH). We also found an interesting association of hand use preference with the clockwise versus counterclockwise scalp hair-whorl rotation. We suggest that individuals with the right gene are RH and develop clockwise hair whorls, but individuals with the recessive allele are 50:50 in hair whorl orientation. We previously proposed that human brain and visceral organs laterality might be controlled by the Somatic Strand-specific Imprinting and selective chromatid/strand Segregation (SSIS) model. This model predicted a chromosome-specific, nonrandom WW:CC segregation phenomenon in which both older "Watson" strand-containing chromatids form a homologous pair of chromosomes and are delivered in mitosis to one daughter cell and the older "Crick" strand-containing chromatids are delivered to the other daughter cell. This was proposed as a mechanism for cellular differentiation to produce non-equivalent daughter cells in mitosis. We have now established the existence of such biased strand segregation phenomenon in mice cells concerning chromosome 7 segregation. Interestingly, this segregation pattern is regulated so that there is directed segregation in some cell types but random segregation in others. In future experiments, we will identify the mechanism of biased strand segregation of this chromosome and we will also determine whether other chromosomes are likewise subject to the cell type-regulated segregation process.